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  3. Since the Hawaiian Islands have never been connected to other landmasses, the great variety of plants in Hawaii must be a result

Since the Hawaiian Islands have never been connected to other landmasses, the great variety of plants in Hawaii must be a result

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问题     Since the Hawaiian Islands have never been connected to other landmasses, the great variety of plants in Hawaii must be a result of the long-distance dispersal of seeds, a process that requires both a method of transport and an equivalence between the ecology of the source area and that of the recipient area.
    There is some dispute about the method of transport involved. Some biologists argue that ocean and air currents are responsible for the transport of plant seeds to Hawaii. Yet the results of flotation experiments and the low temperatures of air currents cast doubt on these hypotheses. More probable is bird transport, either externally, by accidental attachment of the seeds to feathers, or internally, by the swallowing of fruit and subsequent excretion of the seeds. While it is likely that fewer varieties of plant seeds have reached Hawaii externally than internally, more varieties are known to be adapted to external than to internal transport.
The author of the passage is primarily concerned with ______.
选项 A、discussing different approaches biologists have taken to testing theories about the distribution of plants in Hawaii
B、discussing different theories about the transport of plant seeds to Hawaii
C、discussing the extent to which air currents are responsible for the dispersal of plant seeds to Hawaii
D、resolving a dispute about the adaptability of’ plant seeds to bird transport
答案B
解析 本文作者主要讨论各种有关把植物种子输送到夏威夷的理论。首先，生物学家们认为，由于海洋和气流的缘故，植物的种子被输送到夏威夷；其二，漂浮实验以及气流低温实验结果对有关假设提出质疑；其三，鸟类最有可能把种子带到夏威夷。
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